1. Field of the Invention
The present invention relates to a loudspeaker combined with a picture image reproducer is so constructed as to reproduce a center channel signal in a multichannel sound signal for a movie or the like as a principal object, and more particularly, to realization of reproduction in which a sound image and a picture image coincide with each other utilizing characteristics in acoustic psychology.
2. Related Art Statement
In recent years, impressive and powerful movies or the like have been increasingly enjoyed, even in homes upon being reproduced by combining a large screen television (TV) and a sound reproducer for reproducing a multichannel sound signal, for example, a Dolby prologic.
As shown in FIG. 16, a conventional multichannel sound reproducer combined with such a picture image reproducer comprises a loudspeaker 2L for reproducing a left channel signal and a loudspeaker 2R for reproducing a right channel signal which are located on the left and right sides of a TV 5 placed ahead of a viewer 6, a loudspeaker 11 located on the TV 5 for reproducing a center channel signal, and two loudspeakers 4R and 4L located at the sides of the viewer 6 for respectively reproducing surround signals. And these apparatuses are arranged in a room confined by four walls WF, WB, WR, and WL, as typically shown in FIG. 16.
In the multichannel sound signal reproducer, the loudspeakers 2L and 2R respectively reproduce left and right channel sound signals, and the loudspeaker 11 mainly reproduces dialogues spoken by characters on a TV screen, for example. The normal location of the lines is greatly improved by providing the loudspeaker. Further, the loudspeaker 4L and 4R reproduces a surround channel signal representing reverberations and a reflected sound. A sound field at which the viewer 6 feels as if he or she was present is formed by sounds radiated from the loudspeakers.
In the above-mentioned conventional construction, however, the center channel signal is reproduced from the loudspeaker 11 located on the TV 5, so that a sound image is formed around a position indicated by B, as shown in FIG. 17. On the other hand, a picture image is reproduced by the TV 5 under the loudspeaker 11. Therefore, the position of the sound image and the position of the picture image are separated from each other, thereby giving an uncomfortable feeling to the viewer 6.
As a method of solving such points, it is considered that two loudspeakers 12 for respectively reproducing center channel signals are located on both the right and left sides of a TV 5 in the vicinity thereof, as shown in FIG. 18. In such construction, the center channel signals are synthesized upon being respectively radiated from the loudspeakers 12A and 12B located on the right and left sides of the TV 5, so that a sound image is formed in the center (C) between the two loudspeakers 12A and 12B. Consequently, it is possible to perform reproduction in which the positions of the sound image and a picture image coincide with each other.
In the construction shown in FIG. 18, however, when the viewer 6 views a screen of the TV 5 in a position shifted leftward, as indicated by 6a, for example, the sound image on a center channel is also shifted to a position indicated by Ca, thereby giving an uncomfortable feeling to the viewer 6. Further, the loudspeakers 2L and 2R for respectively reproducing the left and right channel sound signals must be respectively located outside the loudspeakers 12, so that large spaces for installation are required on the right and left sides of the TV 5. If there are a lot of loudspeakers on the right and left sides of the screen, the picture image may be visually prevented from being viewed.
In order to avoid such points, JP-A-4-270600 discloses that two loudspeakers 12A and 12B for respectively reproducing center channel signals are arranged above and below a TV 5, as shown in FIG. 19. If the loudspeakers 12A and 12B are thus arranged, a sound image is formed in a position substantially in front of the TV 5 indicated by D, thereby making it possible to perform reproduction in which the positions of the sound image and a picture image coincide with each other. In this construction, however, large spaces for installation are required both above and below the TV 5.
As means for solving the above-mentioned problems, the inventors and others of the present invention have proposed a loudspeaker for reproducing a center channel signal utilizing characteristics in acoustic psychology in JP-A-8-47097 and JP-A-8-130794. In the publications, it is made clear that a particular band in a frequency band of not less than approximately 4 kHz, and particularly a band in a range of approximately one octave centered around 6.3 kHz is important in recognizing the positions above and below a sound source as the acoustic characteristics of human beings. The contents proposed in the publications are applications of the characteristics in acoustic psychology and xe2x80x9cEffect of visual priorityxe2x80x9d described in xe2x80x9cExperiments on the interaction between a sound image and a video imagexe2x80x9d published by Komiyama, Nakabayashi, Nikaido, et al. (Material in Society for Acoustic Research, 1981), for example.
In JP-A-8-47097, each of the loudspeakers located above and below a picture image reproducer in the vicinity thereof comprises as main components sound pressure attenuating means for suppressing sound pressure in the vicinity of 6.3 kHz, and a main speaker connected thereto, and further comprises a sub-speaker located, facing in a direction different from the main speaker, and band passing means connected thereto for supplying a frequency band in the vicinity of 6.3 kHz. That is, the loudspeaker is so constructed that a sound having a frequency of 6.3 kHz is removed from the main speaker for reproducing a direct sound, and its band is reproduced as a diffused sound utilizing reflection from a rear wall or the like by the sub-speaker. As a result, the position of a sound source of a center channel signal is not easily recognized. A viewer feels as if a sound image was drawn to a TV screen due to the effect of visual priority and coincided with a picture image.
In this construction, however, when the distance from the rear wall is large or there is no wall, the level of a reproduced sound from the sub-speaker becomes low, so that the level in a high frequency region is liable to be insufficient as the entire reproduced sound. In order to improve this point, it is considered that the sub-speaker is provided on a ceiling surface. As apparent from recent experiments, however, if a sound having a frequency in the vicinity of 6.3 kHz is reproduced toward the ceiling of a room, the viewer feels as if the position of the sound source was not only clarified but also moved further upward.
On the other hand, in JP-A-8-130794, a sub-speaker for reproducing a sound having a frequency in the vicinity of 6.3 kHz and a main speaker for reproducing a sound having a frequency other than the frequency in the vicinity of 6.3 kHz are constructed as separate cabinets, the smaller sub-speaker being located above a picture image reproducer such that a sound radiating axis of its speaker unit is directed backward, and the main speaker being located below the image reproducer. In such construction, it is possible to perform reproduction in which a picture image and a sound image coincide with each other utilizing characteristics in acoustic psychology, as in JP-A-8-47097. However, the construction requires that loudspeakers are located in two positions, so that wiring becomes complicated. Further, the distance from a rear wall is important in order to keep the balance in a frequency band of a reproduced sound, as in JP-A-8-47097.
The present invention has been made in view of the above-mentioned conventional problem, and has for its object to provide, for reproducing a center channel signal, a loudspeaker capable of easily matching a picture image and a sound image with each other without considering the distance from a rear wall and taking a large space for installation, and capable of minimizing visual interference.
In order to solve the above-mentioned problems, according to a first aspect of the present invention, a loudspeaker apparatus for converting a first audio signal to audible sound comprises:
a band suppressor for suppressing a first predetermined band in the first audio signal to produce a second audio signal;
a first speaker unit connected to the band suppressor for converting the second audio signal to a first sound wherein the first predetermined band is suppressed;
a band filter for passing a second predetermined band in the first audio signal to produce a third audio signal;
a second speaker unit connected to the band filter for converting the third audio signal to a second sound wherein the second predetermined band is audible; and
a dispersing unit located over the second speaker unit for diffusing the second sound therefrom.
As is apparent from the above, according to the first aspect, since the level in the vicinity of the first predetermined band of the second is suppressed, the viewer does not easily recognize the position of a sound source in terms of acoustic characteristics. On the other hand, a sound having the second predetermined band is radiated sideward, and is reflected from the walls or the like, to reach the viewer. Consequently, the viewer recognizes the second sound as an indirect sound, so that the position of the sound source is also difficult to recognize.
According to a second aspect, in the first aspect, a loudspeaker apparatus is located above an image reproducer in the vicinity thereof for exclusively reproducing a center channel signal in a multi-channel sound signal for a movie or the like as a principal object.
As is apparent from the above, according to the second aspect, a sound image is drawn to a screen due to the effect of visual priority, so that the viewer feels as if the sound image and a picture image coincide with each other.
According to a third aspect, in the loudspeaker apparatus of the first aspect, the band suppressing unit is comprised of a dip circuit; and the band filter is comprised of a band-pass circuit.
According to a fourth aspect, in the loudspeaker apparatus of the first aspect, the first speaker unit and the second speaker unit are arranged such that acoustic radiating axes thereof are parallel to each other.
According to a fifth aspect, in the loudspeaker apparatus of the fourth aspect, the first speaker unit and the second speaker unit are located on one plane.
As is apparent from the above, according to the fifth aspect, since the first and second speaker units can be mounted on the same plane, it becomes easy to process the cabinet and assemble the entire loudspeaker.
According to a sixth aspect, in the loudspeaker apparatus of the first aspect, the first speaker unit and the second speaker unit are arranged such that acoustic radiating axes thereof are perpendicular to each other.
According to a seventh aspect, in the loudspeaker apparatus of the sixth aspect, the first speaker unit is located on a first plane; and the second speaker unit is located on a second plane perpendicular to the first plane.
According to an eighth aspect, in the loudspeaker apparatus of the first aspect, the first and second predetermined band are the same.
According to a ninth aspect, in the loudspeaker apparatus of the eight aspect, the first and second predetermined band are in a range of approximately a half to two octaves and are not less than 4 kHz.
According to a tenth aspect, in the loudspeaker apparatus of the eight aspect the first and second predetermined bands are in a predetermined range centered around 6.3 kHz.
According to an eleventh aspect, in the loudspeaker apparatus of the first aspect, the dispersing unit comprises a sound reflecting member spreading along with a plane perpendicular to the acoustic radiating axis of the second speaker unit from the side of the acoustic radiating axis to reflect the second sound at least one time therein, the sound reflecting member being comprised of a first top plate and first and second side walls extending by a predetermined length longer than a half of sound wave length corresponding to the second predetermined band to part from each other with a first predetermined angle.
According to a twelfth aspect, in the loudspeaker apparatus of the eleventh aspect, the dispersing unit further comprises a sound diffusing unit having a second top wall and third and fourth side walls connected to the first top wall and first and second side wall, respectively, on the distal end thereof with respect to the acoustic radiating axis for diffusing the third sound in various directions, the third and fourth side walls being parted from each other a second predetermined angle.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.